Bone is a complex tissue, which continuously undergoes renewal and repair, a process termed “bone remodeling.” Two major cell types responsible for bone remodeling are osteoclasts, which resorb bone, and osteoblasts, which form new bone. Bone remodeling is regulated by several systemic hormones (e.g., parathyroid hormone, 1,25-dihydroxybitamin D3, sex hormones and calcitonin), and local factors (e.g., nitric oxide, prostaglandins, growth factors and cytokines). When resorption and formation of bone are not coordinated and bone breakdown overtakes bone building, osteoporosis results. Osteoporosis is also caused by other conditions, such as hormonal imbalances, diseases, or medications (e.g. corticosteroids or anti-epileptic agents).
Compounds that modulate bone remodeling process, either by inhibiting bone resorption or activating bone formation, have the potential for enhancing bone growth, and can be used to treat osteoporosis.